There has been conventionally used an air cleaner filter which is set in a house and a cabin filter which is installed in an inner portion of an air conditioner within a passenger room of a motor vehicle and an air cleaner installed in a ceiling within the passenger cabin or on a panel at the back of a rear seat so as to clean the indoor air, and which clean outdoor and indoor air. And in this cabin filter or air cleaner, a filter element is used in accordance with an aspect that an air filter base material including a gas decomposing particle or a gas adsorbing particle serving as a gas removing particle is pleated.
In the case of the filter element mentioned above, if the gas removing particle is covered with dust or the like, there is a problem that the gas removing performance is lowered, and the gas removing service life becomes shorter. Accordingly, there is devised such as to efficiently operate functions for deodorizing and removing harmful gas by the gas removing particles after previously removing the dust by a filter element for removing the coarse dust, by laminating or integrating the filter media for removing the coarse dust and a base material including the gas removing particle. As the filter element mentioned above, for example, there has been known a deodorant filter material unit in patent document 1.
However, if the filter media for removing the coarse dust is laminated on the base material including the gas removing particles, a pressure loss of the filter element becomes too large, so that there is generated a problem that an energy cost of the air cleaner or the like becomes high or the gas removing function can not be sufficiently achieved. Accordingly, the filter media for removing the coarse dust is required to have a dust removing efficiency as high as possible and to have a filtering service life as long as possible, in addition to making a pressure loss as small as possible so as to secure a high air flow rate.
If a filter material for removing a coarse dust having a small thickness is used for the requirement, there is obtained an advantage that the pressure loss of the filter element is reduced, and the high gas quantity can be secured. However, there is a problem that a space holding the dust is reduced and the filtering service life of the filter element is shortened.
Further, in the case that the filter material for removing the coarse dust having a large thickness is conversely used, there is obtained an advantage that the space holding the dust is increased and the filtering service life is elongated. However, on the contrary, there is a problem that the pressure loss of the filter element becomes high, the energy cost is increased and the high air flow rate can not be secured.
Patent Document 1    Japanese Unexamined Patent Publication No. 11-254958